The long-term objective of this proposal is to understand the role of the K+CI- co-transporter, KCC4, in hormonal and dietary control of distal colon K+ reabsorption and how it is used regulating whole body K+ homeostasis. An antibody against rat KCC4 will be characterized and used to study cellular expression of this transporter along the proximal to distal axis of rat colon. The specific aims of this proposal include: 1) fully characterize and optimize an anti-KCC4 antibody to maximize its effectiveness in detecting and localizing KCC4 expression in rat; 2) perform real time PCR, Western blotting and immunolocalization studies to examine expression of KCC4 mRNA and protein in rat distal colon epithelia; and 3) compare effects of dietary restriction of K+ and Na+ on expression of KCC4, KCC1 and colonic H/K-ATPase. These techniques will be brought back to the Fellows home campus, an hispanic-serving institution, where they will be used to train (minority) students who are interested in careers in the health professions and/or biomedical research. It is anticipated that a long-term collaboration will be established between the Fellow and the Sponsor, further helping to track these students to research careers at a major doctoral granting institution.